For the following circuit I have some questions: **broken link removed**
(1) Is this oscillator?
(2) Does it work on the battery voltage (5v DC) Or needs to i/p signal for trigger?
(3) How the freq of oscillation can be calculated?
If R7 isn't connected to 0V then it might as well not be there.
It's possible to make an oscillator with two gates but it isn't stable at high frequencies but if all you want to do is flash an LED or make a piezo transducer go beep, it'll be fine.
The circuit you posted is wrong, here's the correct way of doing it. **broken link removed**
There's nothing wrong with that circuit, it's just totally different to the original poster's which wouldn't work and removing the R7 0V connection would've effectively remove R7 from the circuit.
Hi
Here is the main circuit (it function as when you whestile it produce beep beep ) **broken link removed**
I know that gates 5 , 6 and 1 , 2 are oscillators stage
but gates 4 amd 3 , I don't know what they are do?
another question: why D1?
thanks alot
Look at devices 3 and 6. If the output of device 3 is high, it forces the input of device 6 high, and no oscillation can occur. If, however the output of device 3 is low, then theoretically, the output of device 6 is virtually "open" and the oscillator comprised of dev. 5 & 6 is allowed to operate. Now, that portion feeds devices 1 & 2 in an identical manner.
Look at devices 3 and 6. If the output of device 3 is high, it forces the input of device 6 high, and no oscillation can occur. If, however the output of device 3 is low, then theoretically, the output of device 6 is virtually "open" and the oscillator comprised of dev. 5 & 6 is allowed to operate. Now, that portion feeds devices 1 & 2 in an identical manner.
They finally make Beep, Beep. D1 does exactly the same thing as I described for D3. It either forces the state of the next gate's input, or else allows the next network to determine it's own input state. Since each gate pair have a feedback path, they are capable of determining their state. What do you think the state of device 4 is if the diode has the full 9V on it's cathode? How bout 0V?
The circuit posted by the original power beeps when it picks up a high pitched sound.
The piezo transducer is used both as a microphone and a speaker.
Tr1 and Tr2 form an amplifier and bandpass filter to select the frequency of human whistling.
Gates 3 and 4 form a timer which enable the beeper when triggered by a whistle.
Gates 5 and 6 form a low frequency oscillator which disable the audio oscillator when the output is high.
Gates 1 and 2 form an audio frequency oscillator.
There must be a way to stop it from self triggering, i.e. when it's beeping it doesn't hear its own beep, I assume it detects a different frequency whistle than the sound it produces.
I understand that Tr1 and Tr2 form an amplifier, but how they form a bandpass filter? Can you please explain it.
The human whistling freq is about 1800 to 2100 Hz. I try it in a multisim program and it show a highpass filter!
Gates 3 and 4 form a timer which enable the beeper when triggered by a whistle.
Is T for the Timer = 1.1 R7*C7 = 1.1* 2.2* 1= 2.4 sec.
is the timer on for T sec then off?
Why that timer proceeded by D1? is it to pass the negative part of the voice signal?
Why R6?
Gates 5 and 6 form a low frequency oscillator which disable the audio oscillator when the output is high.
I tried it now using Audacity program. I can whistle as high as 2.5kHz. But a piezo transducer is sensitive at a few resonant frequencies above 3kHz.
My daughter bought a cheap "keys-finder" product. It beeped whenever she talked and when the TV was playing but I couldn't trigger it by whistling loudly near it.
The two transistors have three low-value coupling capacitors which are a highpass filter and C6 is a lowpass filter. Both make a very simple bandpass filter.
Thank you guru, You already have solved the first problem superbly, I got the idea.
You have mentioned that "The two transistors have three low-value coupling capacitors which are a highpass filter and C6 is a lowpass filter" What are the values recommended by you for the caps to make the circuit better?
To Hero999
Thank you very much for your interest
But you did not answer my question about the diode D1.
I think the voltage at the collector of transistor T2 is a DC voltage + the amplified signal. Those enter the diode, Is the diode passind only the negative part of the amplified signal and blocking both the DC and the +ve part?
Thank you guru, You already have solved the first problem superbly, I got the idea.
You have mentioned that "The two transistors have three low-value coupling capacitors which are a highpass filter and C6 is a lowpass filter" What are the values recommended by you for the caps to make the circuit better?
To Hero999
Thank you very much for your interest
But you did not answer my question about the diode D1.
I think the voltage at the collector of transistor T2 is a DC voltage + the amplified signal. Those enter the diode, Is the diode passind only the negative part of the amplified signal and blocking both the DC and the +ve part?